An issue was discovered in PHP through 7.2.2. The php-fpm master process restarts a child process in an endless loop when using program execution functions (e.g., passthru, exec, shell_exec, or system) with a non-blocking STDIN stream. This allows a remote attacker to generate a DoS on Shared Hosting Services, performed by this php-fpm master process consuming 100% of the CPU and disk space with a large volume of error logs. References: https://bugs.php.net/bug.php?id=70185 [php 5.4] https://bugs.php.net/bug.php?id=75968 [php 7.2]
Created php tracking bugs for this issue: Affects: fedora-all [bug 1547726]
Statement: The Red Hat Product Security Team does not consider this issue as a security flaw because specially crafted PHP scripts (containing embedded operating system commands) are required to trigger this flaw.
Correction to "containing embedded operating system commands": no embedded operating system commands are needed, only 2 php scripts are needed to CPU-DOS a shared hosting server without leaving a trace where the high load comes from, making it impossible to detect which hosting customer is to blame for. copy from PHP Bug #75968: Script 1: <?php stream_set_blocking(STDIN, false); echo "Blah"; ?> Script 2: <?php passthru('/usr/bin/php /path/to/1.php'); ?>